I have a couple of cast iron sheets in the oven and heat them up with the oven. Tend to go full steam for the first 20 mins and then reduce it (oven has 0-3 settings for steam). I want the bread to go onto a hot sheet in a hot steamy oven to get as instantaneous rise and expansion as possible.
What level of steam do you use? and do you put a stone/steel in to preheat?